A plastic is a polymer, which in turn is an organic macromolecule created by polymerization. Polymerization links simple molecules together, creating chains that may have several thousand elements.
An example:
__ __
| |
H H | H H |
\ / | | | |
C = C Ethene is polymerized to | - C - C - | Polyethene
/ \ | | | |
H H | H H |
| |
|_ _| n
The graphic above is the standard way of displaying polymers. The links left and right of the carbon atoms connect to the next carbon atoms in the chain. The n in the lower right corner is the number of elements in the chain.
There are three types of plastics: duroplasts, elasts and thermoplasts.
- Duroplasts are hard and inflexible at any temperature. Their structure decomposes when they are heated.
- Elasts are elastic at normal temperatures, they reassume their original form after bending. They are destroyed as well when heated.
- Thermoplasts are relatively hard, but become more flexible when heated, and can melt without the molecular structure being destroyed.
Polymers, or plastics, are one of the most important materials today. There are many different polymers with different flexibility, price, weight, flammability and toxicity. This makes plastics suitable for a wide range of products. The teflon in frying pans, for example, is similar to the substance PET bottles are made of.
A selection of important plastics:
These are all thermoplasts, except for teflon, which is a duroplast.